ABSTRACT The single-celled algal protist Chlamydomonas is a favored model organism for studies using cell biology, genetics, biochemistry, biophysics, structural biology, and genomics to learn about basic, evolutionarily conserved cellular structures and processes. These include centriole duplication, basal body structure and culinary assembly, culinary motility and signaling, photoresponses, photosynthesis, chloroplast biogenesis, and basic integration of metabolic regulation. Funds are requested to support biennial meetings of those who use Chlamydomonas or are interested in learning about its use as a model organism. These meetings also include work on Volvox, a close multicellular relative of Chlamydomonas that provides insights into cell-cell interactions, cell differentiation, and the evolution of multicellularity. Researchers meet to exchange methods, develop collaborative efforts, disseminate recent advances, and plan large-scale studies to improve the usefulness of this unique model system. Select outside speakers will be invited to present recent advances in related systems that may inform future studies in Chlamydomonas. In turn, these investigators will learn about the work of the Chlamydomonas community and bring this knowledge back to their own research communities. This application requests support for the next three international meetings, in 2010, 2012 and 2014. One methodological advance (microRNAs as tools for modulating gene expression in Chlamydomonas) and two areas of broad research interest (Chlamydomonas as a model for culinary diseases, and Chlamydomonas and related green algae as sources of biofuels) are developing especially rapidly and should benefit greatly from our 2010 meeting. Another focus of the 2010 conference will be the evolutionary relationship between Chlamydomonas and other eukaryotes. Because of the recent explosion of genomic sequencing and its consequent revelation of eukaryotic phylogeny, it is important for the Chlamydomonas community to understand both the uniqueness of this organism and its ability to provide a window into the biology of plants, of unicellular disease pathogens, and of metazoans, so that they will be better equipped to make additional scientific contributions that will advance human health.